The rear window of a pickup truck can be made such that at least part of the window will slide back and forth. In so doing, an individual in the cab of the truck can have access to the bed of the truck and/or allow air to enter the cab by opening the back window. In some instances, the rear window can be powered such that at least part of the back window slides back and forth through the use of an electrical and/or mechanical device. In such instances, a sliding window pane will typically slide at least partially within a window guide rail that is at least partially encased within a window casing. In addition, the window casing can be made by injection molding of a polymer resin.
Heretofore back window assemblies have used caps at the ends of the window guide rail. The caps can prevent the window casing material from flowing into the guide rail during injection molding of the casing and before the casing material has cured into a solid structure. However, such caps have previously not provided simple and direct access from a window pane sliding system to the sliding window pane. As such, a power sliding window assembly that has an improved cap would be desirable.